It has long been known to employ arrangements, in particular in grinding or truing machines, which comprise an acoustic transducer, preferably of the piezo-electric type intended to detect the acoustic emission which is generated when the grinder touches the workpiece, the signal thus obtained being amplified and thereafter employed to reduce, if necessary to zero, the relatively high speed employed during the approach phase. Such arrangements are described particularly in Swiss patent Nos. 316.871, 585.609 and French patent Nos. 1.371.394 and 1,562.799.
At the same time these known arrangements present a disadvantage in that the sound generated by the tool when it comes into contact with the workpiece, is scarcely differentiated in intensity and frequency from the parasitic noises produced by the machine, for example the noise of bearings, gears, pneumatic or hydraulic drive means, etc. to the extent that satisfactory operation of the arrangement may not always be guaranteed.
The purpose of the invention is to provide a method and an arrangement for controlling the advance of a tool in a machine tool which avoid the previously mentioned difficulties.